In order to save a building and human lives from house fire, it is effective to install a fire detector that detects the occurrence of fire at an early stage and gives an alarm. For this purpose, when the fire detector installed in a monitored region detects fire, the fire detector outputs an alarm signal to sound an alarm bell or an alarm speaker, thereby notifying the occurrence of fire.
However, in a building having high sound insulation such as a hotel, even when the alarm bell installed on an access is sounded, the alarm sound is not easily audible by users within living rooms. To solve this inconvenience, a sounder (a base sounder) that is directly fitted to the fire detector within the living room and generates alarm sound based on the output from the fire detector is put into practical use. For example, U.S. Pat. No. 6,362,726 discloses a base sounder that can be fitted to a fire alarm system. According to such base sounder, the alarm sound can be output at the same position as the fire detector within the living room, thereby more securely achieving the fire alarm.
A configuration of the above conventional base sounder is explained. FIG. 21 is a vertical cross-sectional view of the conventional sounders installed on the ceiling surface. As shown in FIG. 21, the conventional base sounder 100 is fitted to a ceiling surface 102 via a fitting base 101. A fire detector 103 is connected to a lower end of the base sounder 100. Electric constituent elements such as a circuit substrate 104 and a piezo element 105 are accommodated inside the base sounder 100. Alarm sound output from the piezo element 105 is discharged to the outside of the base sounder 100. A screw hole 106 being passed through is formed in the base sounder 100. The base sounder 100 is fixed to the fitting base 101, by having a long screw 107 inserted into this screw hole 106 and screwed into the fitting base 101. The fire detector 103 is fixed to the base sounder 100, by having an upper end of the fire detector 103 latched with the lower end of the base sounder 100.
Wiring holes 108 and 109 being passed through respectively are formed at approximately the center of the plane surface (a position near the center of the plane surface approximately horizontal with the ceiling surface 102 as the installation surface (hereinafter, “the position near the center”)) of the fitting base 101 and the base sounder 100, respectively. A lead wire 110 led out from the ceiling surface 102 is drawn to reach the lower surface of the base sounder 100, via the wiring holes 108 and 109. The lead wire 110 lead out in this way is connected to a connection terminal 111 provided on the lower surface of the base sounder 100, with a screw. This connection terminal 111 is connected to a circuit substrate 104, thereby supplying power to each electric constituent element of the base sounder 100. A connection terminal 112 of the fire detector 103 is connected to the connection terminal 111, thereby supplying power to each part of the fire detector 103.    Patent Document 1: U.S. Pat. No. 6,362,726